1. Field of the Disclosure
The subject disclosure relates to drilling turbines, and more particularly to an improved steerable drilling turbine having modular components.
2. Background of the Related Art
In oil exploration, drilling is an established method of creating a bore-hole through the earth. Many drilling machines are turbines powered by a turbine blade system. Impulse type drilling turbines are driven by a fluid at atmospheric pressure, while reaction type drilling turbines are driven by fluid pressurised to above atmospheric pressure, possessing energy which is partly kinetic and partly pressure. Drilling turbines are often preferred because of the ability to be successfully deployed in steerable drilling applications.
In drilling turbine applications, the drilling turbine is used to transfer the hydraulic power of a drilling fluid being pumped through the drilling turbine into rotational power of a rotor element, which is rigidly attached to a drive shaft system. Ultimately, the drive shaft system is connected to a drilling bit for the explicit purpose of boring through the earth's structure such as rock. The hydraulic fluid is often referred to a drilling mud. The typical drilling turbine is configured as a 20-30 foot long pair of matching helixes with one helix being the stator and one helix being the rotor.
Despite many advances, there are problems associated with turbine drilling. For example, turbine life can be undesirably short due to the abrasive drilling mud and damage from larger particles in the mud flow. Traditionally, once a portion of the turbine is worn out, the entire turbine assembly is replaced. Such a replacement is a costly approach.
The conventional drilling turbine also has low efficiency, e.g., 40%, because of the large tip clearances that are required. The tip clearance is needed to allow for shocks and bending of the rotor/stator assembly that are normal during operation. Further, as the drilling turbines are run at high speed, sealed oil bearings are used. Despite being sealed, it is difficult to prevent ingress of mud and other contaminants that reduce bearing speed, effectiveness and life.
Traditional drilling turbines also use a reduction gearbox that is oil lubricated. The reduction gearbox brings the relatively high working speed of the turbine down to a suitable speed for the cutting tools. This reduction gearbox suffers from similar sealing issues with respect to mud and contaminants as the sealed bearings.